JPH07100603B2 - Composite carbonitride manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a hard carbon material, Ti, Ta, W, Mo composite carbonitride, which is a hard raw material required for the production of an extremely tough and high quality nitrogen-containing cermet. Regarding manufacturing method. The nitrogen-containing cermet made of the composite carbonitride according to the present invention can be effectively used for a cutting tool used under high speed and high feed conditions.

[Conventional technology]

Nitrogen-containing cermets in which carbonitrides such as Ti, Ta, W, Mo, etc. are bonded with metals such as Na and Co are more difficult to cut than conventional cermets that do not contain nitrogen. It is known that the plastic deformation resistance and the heat fatigue resistance are significantly improved (Japanese Patent Publication No. 49-1364).

By the way, in the production of this type of cermet, when sintering is performed in a vacuum, carbonitrides contained in the cermet alloy are decomposed, so-called denitrification phenomenon occurs and the effect of nitrogen addition is reduced, or In addition, the nitrogen gas generated at that time does not sufficiently escape from the sintered body and remains as a bore after sintering, both of which significantly reduce the reliability of the nitrogen-containing cermet as a tool.

Therefore, Japanese Patent Publication No. 49-1364 discloses a technique of suppressing decomposition of nitrides by sintering the thermite in a nitrogen atmosphere instead of in a vacuum. Further, as the nitrogen content increases, the denitrification amount also increases, and therefore, the atmospheric nitrogen pressure needs to be 80 Torr or more to suppress it, but there is a drawback that degassing from the thermite during sintering becomes insufficient. It was

As a method of overcoming this, a method has been proposed in which a composite carbonitride of a metal element contained in the thermite is manufactured in advance, the nitrogen dissociation pressure is lowered, and denitrification during sintering is suppressed as much as possible (for example, Japanese Patent Publication No. −51201 publication).

Furthermore, in order to make the powder of the composite carbonitride into fine particles, an attempt has been made to use an oxide as a starting material, mix it with carbon powder, and heat it in a nitrogen stream (for example, Japanese Patent Laid-Open No. 61-61). -291408, etc.).

In addition, such a conventional method for producing a composite carbonitride is generally performed by an open boat-type continuous furnace in which nitrogen is kept flowing and the boat is sequentially fed. It was

[Problems to be solved by the invention]

However, in the conventional method of producing a composite carbonitride by flowing nitrogen into a mixture of oxide and carbon, free carbon and oxygen remain, and a cermet using the obtained composite carbonitride as a raw material is produced. However, there is a problem in that the sinterability in the sintering process at the time of deterioration is deteriorated, and as a result, the wear resistance and the toughness, which are the characteristics of the tool, are reduced.

The present invention solves this problem by using metal oxide and carbon powder as raw materials to prevent oxygen and free carbon from remaining, and is a fine powder of good sinterability of Ti, Ta, W, Mo composites. The purpose is to propose a method for producing carbonitrides.

[Means and Actions for Solving Problems]

In search of a solution to the above-mentioned problems, the present inventors have conducted a detailed study on the production process of a composite carbonitride using an oxide as a starting material.

As a result, the conventional method of producing a composite carbonitride from an oxide raw material by the open boat feeding method with nitrogen flowing as described above clearly has a simplified manufacturing process, and Since the powder itself is originally fine particles, the resulting composite carbonitride powder is also effective in that it becomes fine particles, but it has been found that the reaction is very complicated. This is because, in addition to the reduction reaction, carbonization and nitriding reactions also occur, and further a solid solution reaction also occurs. With heating, first, the reduction reaction of each oxide proceeds as Co gas generation, and then nitriding and carbonization continue. We have found that the two occur in an overlapping manner.

Therefore, according to this finding, in order to completely remove oxygen, it can be said that the ideal means is to maintain high vacuum up to the reduction end temperature and then supply nitrogen. However, in reality, unless nitrogen is flown, grain growth starts from a certain temperature, and the original purpose of atomization cannot be sufficiently achieved.

In view of these circumstances, the present inventors have made repeated studies on a heating method using an oxide as a raw material, which can achieve both removal of oxidation, prevention of residual free carbon and atomization, particularly atmospheric conditions and temperature conditions. , TiO ₂ , Ta ₂ O ₅ , WO ₃ , MoO ₃ and carbon powder are mixed as a starting material, the mixture is heated in a vacuum, and then nitrogen is supplied into the atmosphere at a temperature of 1200 ° C. or higher and 1500 ° C. or lower. And then 1500 ° C or more and 2100 ° C in the nitrogen atmosphere.
T characterized by holding at the following temperature to react
The present invention, which is a method for producing a composite carbonitride of i, Ta, W, and Mo, has been reached.

In the present invention, Ti, Ta, W, Mo are respectively supplied as oxides of TiO ₂ , Ta ₂ O ₃ , WO ₃ and MoO ₃ , carbon powder is mixed with this, and when this is heat-treated, the reduction reaction is first performed. On the low temperature side where the
Nitrogen supply to the atmosphere is started in the range of up to 00 ° C or lower, and subsequently, heating is performed at 1500 ° C or higher and 2100 ° C or lower in this nitrogen atmosphere to cause carbonitriding reaction and Ti, Ta, W, Mo.
This is a method for obtaining the double carbonitride. Nitrogen atmosphere pressure 30To
It is particularly preferable that the pressure is rr or more and 10 atm or less.

By using the oxide as a starting material in this way, a fine powder is obtained, and since the vacuum is sufficiently maintained during the reduction reaction of the oxide, the oxygen content can be significantly reduced,
Moreover, since oxygen escapes as Co gas, carbon mixed for reduction in addition to the amount of carbon necessary for carbonization also fulfills its role. As a result, a high-quality composite carbonitride containing significantly less residual oxygen and free carbon can be obtained.

Therefore, when a thermite is produced using the composite carbonitride of the present invention, a highly reliable alloy having very good sinterability and excellent cutting resistance in wear resistance, toughness, and heat cracking resistance can be obtained. You can get it.

The general method and the reasons for limitation in the present invention will be described below.

1) Vacuum heating conditions The degree of vacuum is 10 ^-3 Torr or more and 10 Torr or less. If it is less than 10 ^-3 Torr, there is no difference in effect, and if it exceeds 10 Torr, oxygen and free carbon cannot be sufficiently removed. There is no particular limitation on the time for holding in vacuum.

2) Rate of temperature increase 1 to 100 ° C./minute is preferable in the entire temperature range from room temperature (start of heat treatment) to the maximum reached temperature of 1500 ° C. or more and 2100 ° C. or less.
If it is less than 1 ° C / min, grain growth occurs, and if it is more than 100 ° C / min, oxygen and free carbon cannot be sufficiently removed.

3) Nitrogen supply is started at a nitrogen supply start temperature of 1200 ° C or higher and 1500 ° C or lower. When supplied below 1200 ° C, oxygen remains in the composite carbonitride,
Even if the temperature exceeds 00 ° C., if nitrogen is not supplied, grain growth will occur and the hardness of the alloy will be reduced, which is not preferable.

4) Nitrogen atmosphere pressure during heat treatment is 30 Torr or more and 10 atm or less. If it is less than 30 Torr, the effect of refining by nitrogen supply cannot be obtained, and even if it exceeds 10 atm, there is no difference in the effect, and waste is generated in equipment, which is not preferable.

5) Reaction temperature Hold the reaction at 1500 ° C or higher and 2100 ° C or lower in a nitrogen atmosphere to react. If it is less than 1500 ° C, solid solution is not sufficient, which is not preferable, while if it exceeds 2100 ° C, grain growth becomes remarkable, which is not preferable.

6) The holding time at the highest temperature is preferably 10 minutes or more and 5 hours or less. If it is less than 10 minutes, the reduction reaction is insufficient, and if it exceeds 5 hours, grain growth is caused, which is not preferable.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to examples. In each of the examples and comparative examples, the degree of vacuum was measured at a position 20 cm from the furnace into the exhaust pipe.

Example 1 TiO ₂ powder, Ta ₂ O ₅ powder, WO ₃ powder, MoO ₃ powder and C powder were mixed and kneaded with water and granulated, and heated to 1400 ° C. in a vacuum of 0.1 Torr, and then PN ₂ = 400 Torr. Nitrogen was introduced and the mixture was kept at 1600 ° C. for 1 hour to obtain a composite carbonitride A of the present invention. The temperature rising rate from the start of the heat treatment to 1600 ° C was 10 ° C / min.

For comparison, similarly granulated product was heated in a nitrogen atmosphere of PN ₂ = 400 Torr up to 1600 ° C. at a heating rate of 10 ° C./min, and a comparative product B was obtained which was held for 1 hour under these conditions.

Table 1 shows the analysis results of the A and B samples. From Table 1, although the product A of the present invention and the comparative product B have almost no difference in particle size,
It is clearly seen that the product A of the present invention has significantly reduced free carbon and oxygen contents.

To each of the obtained composite carbonitrides A and B, 8 parts by weight of Ni and Co were added, and sintered at 1450 ° C. for 1 hour to prepare a thermite alloy. The obtained alloy had almost no cavities in the alloy obtained by using the product A of the present invention as a raw material, whereas the alloy B of the comparative product B
A06 type (carbide tool association standard CIS
006B-1983).

Example 2 Ti: Ta: Wi: Mo = 0.84: 0.03: 0.07: 0.03, C: N = 0.52: 0.48 Metal or oxide as shown in Table 1 so that the ratio of non-metal component / metal component is 1.0. Materials, carbides, and carbonitrides were mixed, and each sample was vacuum heated to 1380 ° C at 0.2 Torr, then 1380 ° C.
Nitrogen was introduced at PN ₂ = 1 atm from and the temperature was maintained at 1600 ° C. for 1.5 hours. The temperature was raised from the start of heat treatment to 1600 ° C at 12 ° C / min. Table 2 shows the analysis results of the obtained composite carbonitrides of the present invention product C and the comparative products D and E.

As a result, the product C of the present invention has a much smaller particle size than the comparative product D using the metal powder without using the oxide raw material, and the free carbon amount,
Both the amount of oxygen is reduced, and although the amount of oxygen is slightly higher than that of the comparative product D made of carbonitride or carbide,
It can be seen that the free carbon is comparable and the particle size is very small. That is, it was confirmed that the product of the present invention was the finest.

Example 3 Powders of TiO ₂ , Ta ₂ O ₅ , WO ₃ , MoO ₃ and C were blended as shown in Table 3 and heated, reduced and carbonitrided. At this time, the rate of temperature rise is 12 ° C / min, the degree of vacuum is 0.1 to 0.5 Torr, and PN ₂ is all 1
Atmospheric pressure was used. The present invention products F to I and the comparative products J to O obtained
Table 3 also shows the results of the analysis of the composite carbonitride.

Example 4 The composite carbonitrides A, B, E, H, M and N obtained in Examples 1 to 3 were used as raw materials, and Ni and Co were added thereto in an amount of 10% by weight, mixed and pressed. , 1420 ℃, PN ₂ = 3 Torr under nitrogen atmosphere 1
A cermet alloy was produced by time sintering. The obtained alloys are designated as P, Q, R, S, T and U, respectively. The hardness and transverse rupture strength of each alloy are shown in Table 4.

Furthermore, using raw materials E and N, Ni and Co are used to improve hardness.
Were added in an amount of 7 wt% each and sintered at 1450 ° C. and PN ₂ = 5 Torr for 1 hour to obtain alloys V and W. The hardness of these alloys,
The transverse rupture strength is shown in Table 5, but the transverse rupture strength was remarkably reduced.

Next, a cutting test was performed on the alloys P to W under the following conditions. The test results are shown in Table 6, and the alloy made from the composite carbonitride of the present invention is excellent in any of the items such as flank wear amount, number of defects in interrupted cutting, and number of thermal cracks generated in interrupted milling cutting. You can see that

Condition 1 Continuous cutting Work material S45C (H _B = 260) Cutting speed 200m / min Feed 0.36mm / rev Depth of cut 1.5mm Chip shape SNGN120408 Holder FN11R-44A Cutting time 10 minutes Condition 2 Intermittent cutting Work material SNCM439 (H _B = 280), 4-groove material Cutting speed 100m / min Feed 0.25mm / rev Cut 2.0mm Chip shape SNGN120408 Holder FN11R-44A Cutting time up to loss. Up to 2 minutes.

Condition 3 Milling intermittent cutting Work material SCM435 (H _B = 250) 80 mm × 200 mm × square material Cutting speed 250 m / min Feed 0.14 mm / blade cut 2.0 mm Chip shape SNGN120408 Holder DNF4160R Cutting time 10 minutes [Effects of the Invention] As described above, the production method of the composite carbonitride of the present invention is a fine powder, and a high-quality composite carbonitride of Ti, Ta, W, Mo with significantly less oxygen and free carbon. Is obtained. Furthermore, when a thermite is produced by using the powder of the composite carbonitrides of Ti, Ta, W, and Mo according to the present invention, the sinterability is very good, and the cutting tool characteristics are extremely excellent in wear resistance, toughness, and heat crack resistance. It has the effect of becoming an excellent alloy.

Claims (2)

[Claims] 1. TiO ₂ , Ta ₂ O ₅ , WO ₃ , MoO ₃ and carbon powder are mixed as a starting material, and the mixture is heated in a vacuum.
Ti, Ta, W, characterized by starting nitrogen supply into the atmosphere at a temperature of 00 ° C or more and 1500 ° C or less, and subsequently maintaining the temperature at 1500 ° C or more and 2100 ° C or less in the nitrogen atmosphere to cause the reaction.
Manufacturing method of Mo composite carbonitride. 2. The nitrogen atmosphere pressure during the heat treatment is 30 Torr or more.
T described in claim 1 at 10 atm or less
Manufacturing method of i, Ta, W, Mo composite carbonitride.